Cross zoned works, but personally I like double interlocked over cross zoned single interlock when you are discussing mitigation of damage.
Cross zoned will not help 'detect' a wider range of fires, it helps 'reduce' the amount of false activations. The more fire signatures you require (ie. Heat, smoke, IR, etc) prior to activation, the less false activations you will have. For example, a welders torch will activate both a heat detector and sprinkler (seen it), but not likely a photoelectric smoke detector and a sprinkler. So you add smoke detection as a way to mitigate non-fire heat sources from tripping the system. There is a good range of smoke detector types (ie photo, ionization, air sampling, etc) and fire alarm program adjustments (ie. Alarm verification, dirty, etc.) that can help reduce false activations. One type of detection that seems good, at least on paper, is video detection. But I can't confirm field success. Duane Johnson, PE Design Manager Strickland Fire Protection 5113 Berwyn Road College Park, MD 20740 301-474-1136 Office 301-455-0010 Cell -----Original Message----- From: Sprinklerforum [mailto:[email protected]] On Behalf Of Steve Leyton Sent: Friday, November 13, 2015 12:37 PM To: [email protected] Subject: Cross zoned preaction detection Does anyone have any strongly held opinions about cross-zoning of detectors for single-interlock preaction systems? I haven't done one, and have usually fallen back on double-interlock when there is a heightened concern about accidental activation (earthquakes and all that). My understanding is that when two different types of detectors are cross-zoned, it can help to detect a wider range of fires that may grow out of the incipient stages at different speed and/or with different release characteristics. And cross-zoning with the same type of detector can give a heightened level of fail safety, so that seems more comparable to double-interlock. I'm interested in hearing any suggestions, opinions of the value of this design (or not) and good or best practices. Steve Leyton _______________________________________________ Sprinklerforum mailing list [email protected] http://lists.firesprinkler.org/listinfo.cgi/sprinklerforum-firesprinkler.org _______________________________________________ Sprinklerforum mailing list [email protected] http://lists.firesprinkler.org/listinfo.cgi/sprinklerforum-firesprinkler.org
